Pacific Quiet: BC Ferries’ Journey to Protect West Coast Whale Habitats

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West Coast Ferries

Many ferry routes criss-cross Canada’s Pacific coast, including those operated by BC Ferries, the provincial ferry service provider. Other routes are operated by Alaskan and Washington state ferry providers and independent operators. Ferries range in size from small passenger-only vessels covering short routes in sheltered waters to large ships that can carry hundreds of vehicles and thousands of passengers over long distances. Many of these ferries transit through areas designated as critical habitat for marine mammals such as the Southern and Northern Resident killer whales. The “Quieter ferries in critical whale habitat on Canada’s West Coast” infographic displays route data gathered from the different ferry operators as well as critical habitat areas from map layers created by Fisheries and Oceans Canada.

Quiet Vessel Initiative projects contributing to quieter ferries

Propeller Noise Correlation for Ferries

Forming part of a more extensive underwater radiated noise control program, BC Ferries and Det Norske Veritas (DNV) Canada created a multi-phase Quiet Vessel Initiative project to test different propeller designs to reduce underwater noise from ferries while maintaining vessel efficiency.

During Phase I, the team used 3D hull form geometry to model the wake field, propeller geometry to model hydrodynamic and cavitation performance, and computer simulations to explore different parameters such as operating conditions, ship speed, propeller pitch, blade number and load, and Revolutions Per Minute (RPM) and their noise impacts on three classes of vessels used by BC Ferries. Classes refers to different types or categories of ships, distinguished by size, purpose, and capacity. The simulation was run several times to assess different propeller designs and their impacts on noise and efficiency. Initial findings showed propeller design changes could reduce underwater noise between 7 to 10 decibels (dB). However, this noise reduction came with a substantial reduction in efficiency, between 2.5% to 4%, which increases greenhouse gas emissions and operating costs.

In Phase II, the team considered the impact of off-design conditions (i.e., vessel speed reductions when the vessel nears and holds in dock) on underwater noise and greenhouse gas emissions. With speed reductions, one vessel class increased noise, highlighting the importance of designing controllable-pitch propellers that can be adapted for most operating conditions. Other types of vessels did not experience the noise increases to the same extent, but the findings concluded that all variable-pitch propellers will have cavitation issues if the pitch is sufficiently reduced for slowing down. The team noted the importance of identifying the relevant operating conditions during the design stage to optimise the propeller for both propulsion efficiency and reduced underwater noise emissions.

Phase III modelled the underwater radiated noise generated by a propulsion system with azimuth thrusters and two different hull forms (one design with one azimuth pod at each end of the vessel and another with two azimuth pods at each end) operating at three different speeds. In these scenarios, the propellers were fixed pitch, meaning underwater noise typically decreases with a reduction in speed. The four-pod system was found to have about three times higher contribution to the total hull resistance in water (and displaced 3% more water) than the two-pod system. When the hull form creates more resistance in the water, the propulsion system has to work harder, creating more noise. The amount of noise emitted by the propellers was around 11 dB(A) higher for the four-pod system and 7 dB(A) higher for the two-pod system, comparing the highest speed (21 knots) with the lowest speed (18 knots). A weighting filter was applied to present the results as dB(A) rather than dB, meaning scaled to match how the human ear perceives loudness rather than presented as absolute sound pressure. If the hull resistance of the four-pod system could be reduced to be the same as the hull resistance of the two-pod system, the propellers for the four-pod system are expected to create less noise.

Phase IV evaluated greenhouse gas emissions and underwater noise performance for three different types of advanced propulsion systems: combinator mode, vertical axis or foil-wheel system, and tandem propulsion system. With newly developed systems, it is more difficult to find data and design examples to conduct such experiments, but with help from the manufacturers and academia, such as the University of Victoria Hydrodynamic Lab, it was possible to predict the greenhouse gas emissions and underwater radiated noise levels for each system.

What are vertical axis propellers?

Vertical axis propellers are relatively new. They are most widely found on tugboats, but Staten Island Ferry uses the system on their ferries in New York City. Seaspan Ferries, a cargo ferry operator on Canada’s Pacific coast, previously investigated this technology for its vessels. Due to the abundance of logs and other debris commonly encountered in the waters around the Strait of Georgia and the broader south-coast region of British Columbia, any vertical axis propellers would need to be protected by propeller cages – an addition that would reduce efficiency and increase noise.

Comparing the three different propulsion systems showed similar relative results, as shown in the table below. The emissions were produced over a typical 15-hour operating day.

Propulsion System Type	Decibels (dB)		Greenhouse Gases (CO2)
	18 knots	21 knots	18 knots	21 knots
Combinator Mode	170 dB	180 dB	27.8 tons	50.7 tons
Tandem Propeller	160 dB	165 dB	26.8 tons	48.8 tons
Vertical Axis Propeller	80 dB	90 dB	25.5 tons	42.4 tons

With each of the three propulsion systems evaluated, the results showed that when travelling faster, the ferries create more noise and more greenhouse gas emissions. Although the vertical axis propeller creates the lowest amount of noise and greenhouse gas emissions, due to maintenance and speed issues, the tandem propeller was deemed the best option.

Overall, the project provided BC Ferries with a solid evidence base for designing quieter, more efficient vessels. The results highlight where noise reductions are most achievable, where efficiency trade-offs arise, and which propulsion options offer the best balance for future improvements.

Hydrodynamic Propeller Noise Monitoring System (HyPNoS)

Working with BC Ferries, Schottel’s Hydrodynamic Propeller Noise Monitoring System (HyPNoS) developed a prototype system to monitor hull vibrations above the propeller. Schottel develops and produces versatile propulsion and control systems for ships. These hull vibration sensors can capture operational, environmental, and wear-related noise variations from the propeller, providing valuable information about the factors influencing noise coming from the vessel.

Capturing this type of noise is important because the vessel’s design – such as placement of the rudder and shape of the hull – influences noise from the propulsion system. Operational conditions, such as vessel speed, rudder angle, shallow water operations, and level of biofouling can also change the amount of noise from the propulsion system.

Schottel used the measurements taken by a permanently installed real-time onboard system of sensors to develop and train an AI-ready algorithm to estimate underwater radiated noise. The measurements from the sensors were compared to hydrophone data to correlate the onboard vibrations with externally measured underwater noise. Once the algorithm had sufficient data (measuring the noise levels from two propeller designs – the original propeller and a quieter design – at different speeds on one of the ferries), the algorithm was able to estimate underwater noise based on vibrations – no need for proximity to hydrophones to quantify underwater noise.

The team is looking to improve the algorithm by incorporating other measurements, such as the vessel location and direction, the propeller’s pitch setting and rotation rate, water depth, and vessel speed. This additional data can provide more accurate underwater noise estimations to guide decisions about which operational changes will reduce underwater noise.

Report on Relationships Between Noise, Vibration, and Underwater Radiated Noise Measurements

AllSalt Maritime worked with BC Ferries to develop a prototype machine-learning-based monitoring system to understand how vibrations relate to underwater noise. This project, Report on Relationships Between Noise, Vibration, and Underwater Radiated Noise Measurements, had two phases.

The first phase took measurements from multiple locations, such as machinery spaces and steering gear compartments, to identify the dominant noise source within the vessel. The second phase focused on understanding that dominant noise source – in this case, the main engine machinery space.

Noise measurements collected from the onboard sensors and external hydrophones calibrated the machine-learning model to estimate underwater radiated noise levels based on vibrations. The project also hoped to measure the relationship between the amount of underwater noise and how efficiently the vessel was operating, but the data in their case was found to be not suitable for this purpose.

Managing Underwater Noise for the Long Term

As BC Ferries expands its fleet to meet growing customer demand and replace ageing vessels, reducing underwater noise has become a focus for both new and existing vessels. One noise-reduction initiative has been to gradually replace propellers and install new variable speed drives on the three Coastal Class vessels, which sail on the primary routes between Vancouver Island and the BC mainland. Although this upgrade enables quieter operations at slower speeds, it has been expensive — both in terms of lost service time and cost of parts. Even so, addressing vessel noise has become a priority. These ships were selected for the upgrade as they were particularly noisy at slower “off-design” speeds, with residents near ferry terminals reporting their windows rattling when the vessels were near or at a berth. In response to complaints, BC Ferries began to shut down the motors when the vessels docked. However, this change caused premature wear-and-tear and led to early replacement of the motor rotors at a cost of $3 million per ship.

As part of its New Major Vessels project, BC Ferries is retrofitting some vessels with diesel-battery hybrid power plants and a propulsion design that is expected to deliver a 63% reduction in underwater noise. Newer concept propulsion systems that may be quieter, more efficient, and produce fewer greenhouse gas emissions are also being explored.

Ordering new vessels is an opportunity to incorporate technology to achieve new priorities, such as reducing underwater noise. In 2024, BC Ferries ordered four new Island Class battery-electric hybrid vessels. Announced in early 2026, the new vessels will be equipped with ABB’s gearless, steerable Azipod® electric propulsion system for greater reliability and reduced noise, compared to traditional propulsion systems. If the vessels can access shore-based charging stations in the future, underwater noise will be further reduced by running on quieter electric battery energy, with up to 70 megawatt-hours of energy storage on board. ABB is a global technology leader in electrification and automation.

Read more about BC Ferries Vessel Noise Management Plan and New Major Vessels project.

This article was prepared by Clear Seas on behalf of Transport Canada as part of the Quiet Vessel Initiative and is part of a four-article series on ferries and underwater vessel noise.

Continue learning about the new discoveries and challenges in making vessels quieter with the other topics in this series here

The Quiet Vessel Initiative is a federally funded program through Transport Canada. Industry partners and researchers interested in potential research and development collaborations to advance innovative solutions in marine technology are invited to contact the Quiet Vessel Initiative team at Marine-RDD-maritime@tc.gc.ca.